1. Field of the Invention
The present invention relates to a vehicle transmission system that has an input shaft brake and disconnect apparatus disposed between a clutch and a multiple speed gear transmission.
2. Background Art
Vehicles are provided with transmissions that provide multiple gear ratios for different power and speed requirements. Many different types of transmissions have been developed, including manual transmissions, automatic transmissions and automated shift transmissions. Automatic transmissions are generally provided for cars and light trucks that provide fully automatic shifting by means of a complex hydraulic and electronic control system. Manual transmissions are simpler and generally require manual disengagement of a clutch and manual movement of a shift lever to engage different gear ratios. Automated shift manual transmissions have been developed that provide the convenience of an automatic transmission but are shifted by means of X-Y shift control motors that move a shift lever in manual transmissions.
Each of the above-described transmission systems may be provided with a synchronizing system that synchronizes a selected gear with a rotating input shaft. The synchronizing system facilitates smooth shifting without the noise and wear caused by a failure of gears to properly mesh as they are engaged. Prior art automated shift transmissions are coupled to an input shaft without a brake being interposed between the clutch and transmission. Synchronizing systems cause input shaft supported gears and output shaft supported gears to rotate at near synchronous speeds. Synchronizing systems add cost and weight to transmission synchronizing systems. Time is required to synchronize rotation of gears and can delay shifting operations.
One approach to permit more rapid shift performance is to provide an inertia brake that is mounted to a transmission power takeoff location. An inertia brake mounted at a power takeoff location can be used to slow shaft rotation and may allow shifts to be synchronized more rapidly. One disadvantage of power takeoff mounted inertia brakes is that such devices add weight to the transmission that can adversely impact fuel economy. Another disadvantage is that assembling a power takeoff mounted inertia brake to the transmission increases the cost of parts and labor. In addition, mounting the inertia brake to a power takeoff location makes that power takeoff location unavailable for other purposes.
In the design of transmissions, of any type, it is an objective to provide capability to shift more quickly and smoothly. By providing quicker shifts, transmission performance and efficiency may be improved.
In some situations, it may be difficult for an operator to perfectly shift between low ratio gears or when it is necessary to shift for performance. For example, when a vehicle is on a steep grade and loaded, the clutch must be disengaged, gears shifted and clutch re-engaged with precise timing. To assist a driver in making these shifts, transmissions are normally provided with synchronizers. Synchronizers delay shifting and can reduce transmission shift performance in difficult situations.
There is a need for a low cost system for providing quicker shifts by allowing more rapid transmission gear synchronization. The present invention is directed to improving transmission performance and providing quicker shifting capability as summarized below.